A supernova is the explosive death of a star, during which it rapidly ejects most of its mass in a brilliant burst of light. In core‑collapse supernovae (Types Ib, Ic, II), massive stars (≥ 8 solar masses) exhaust their nuclear fuel, collapse under gravity, and explode. In Type Ia supernovae, a white dwarf in a binary system undergoes runaway fusion after accreting mass. These events deliver heavy elements into space, leave behind neutron stars or black holes, and power typical shock‑front supernova remnants.
Source: heasarc.gsfc.nasa.gov
12/10/2023

Mu Cephei is a very large star. An M-class supergiant some 1500 times the size of the Sun, it is one of the largest stars visible to the unaided eye, and even one of the largest in the entire Galaxy. If it replaced the Sun in our fair Solar System, Mu Cephei would easily engulf Mars and Jupiter. Historically known as Herschel's Garnet Star, Mu Cephei is extremely red. Approximately 2800 light-years distant, the supergiant is seen near the edge of reddish emission nebula IC 1396 toward the royal northern constellation Cepheus in this telescopic view. Much cooler and hence redder than the Sun, this supergiant's light is further reddened by absorption and scattering due to intervening dust within the Milky Way. A well-studied variable star understood to be in a late phase of stellar evolution, Mu Cephei is a massive star too, destined to ultimately explode as a core-collapse supernova.